Preparation of esters



Patented Aug.14,,1931

J'EZRQME MARTIN All'l) IGNACE 3. KRCHMA, F EAUT'E, INDIAN'A, ASSIGNORS TO COMMERCIAL SOLVEHTS EQBEOlR-ATIOE, GE HA'UTE, INDIANA, A CORPORA- TION 0E MARYLAND ran raaarron or nsrnas No Drawing. Application filed May 1%,

Our invention relates to a method of pre paring esters by passing alcohols over suitable catalysts. More particularly, our process pertains to an improved method of obtaining 5 esters such as ethyl acetate, propyl propion- "ate, butyl butyrate,ethyl butyrate, etc. from the corresponding alcohols or mixture of alcohols.

In the past it has been necessary to prelil pare esters by some such means as esteritication of an ELlCOhOlWltll an acid, or by alcoholysis. In the latter case, it is necessary to make use of an ester which has previously been prepared by esterification, so it is readily 16 seen that the former method has been basic for preparing esters.

We are'aware of the fact that it has recently beenclaimed (English Patent 282,448) that it is possible to obtain condensation products 20 by passing alcohols over suitable catalysts. According to this process, however, which consists of'passing an alcohol, such as ethyl alcohol, atv ordinary pressure and at a temperature of LOO-500" C. over catalysts such as barium oxide, magnesia, lime, manganese oxide, magnesium alcoholate, and sodium alcoholate, there is obtained a mixture of alcohols, acids, esters, acetals, acetone, and acetaldehyde. According to a specific ex ample, when ethyl alcohol Was passed over a catalyst composed of barium oxide, the products consisted of higher alcohols, such as butyl alcohol, acids, esters, such as ethyl acetate, acetals, particularly diethyl acetal, and aldehydes. Our new process of preparing esters has very distinct advantages over this process, in that We are able to obtain much higher yields of esters together with only relatively small amounts of other materials which may readily be separated from the main products and which may be utilized for other purposes, thereby reducing the operating losses to a minimum.

, The formation of esters from alcohols 45. under the influence of certain catalysts at high was. Serial no. erases.

temperatures may be regarded as taking place as follows While We do not know the exact mechanism of the reaction, it appears that the alcohol may be first dehydrogenated into the corresponding aldehyde, two molecules of Which, under certain conditions, then condense to form an ester. T his theory isat least partially corroborated by the fact that Tistschenko (J our. Russ. Phys. Chem. Soc. 38 ii, 355 118, 82550) found that it was possible to obtain esters such as ethyl acetate from acetaldehyde or propyl propionate from propaldchyde, by the use of an aluminium alkoxide catalyst. More recently, modifications of this process have been patented by .lmray (British Patent 12881915) and Mugdan and Herrmann (U. S. Patent 1,459,852). We have found, however, that when an aldehyde and an alcohol are passed under similar operating conditions over catalysts of the character hereinafter described, much lower yields of esters are obtained from the aldehyde than from thecorresponding alcohol. We have also found that the amount of high-boiling material, other than ester, formed during the condensation process is greatly reduced by the use of an alcohol as theraw material.

As has previously been pointed out, esters can be produced from primary alcohols, such as ethanol and butanol, by means of a number of different catalysts. in a copending application, U. S. Serial 278,333 filed May 16, 1928, We have described, catalysts suitable for this purpose, comprising metal uranyl carbonates and metallic silver. NehaveQnow discovered that more I advantageous results may .be obtained by incorporating certain other'materials in our original catalyst mixtures. Qur new and improved catalysts give higher yields, remain active longer and permit the reaction to be carried out at materially lower pressures. Examples of a number of the catalyst compositions which give these improved results are shown in the table below.

Table I Catalyst No. Initial composition of catalyst .i-msm mico.(cootngicois iouiooazxuoma A130M Baal]Oz(( O .Ag CO .Fe(OH) .Al(OH): Adm-M mmo2(comx zooico(oin auomi Al2ll\l BZ12U02(CO3)3.Ag2CO3Cl1CO3.Al(OH):

As will be seen from a consideration of the above table, the essential constituents of these catalysts are metal uranyl carbonate, the term metal being applied generally to metals other than uranium; silver carbonate, a compound of a metal belonging to the first long period of Mendelejeiis periodic table; and a hydroxide of an element or elements occurring in Groups llb to IV inclusive of the periodic table (by Group 11b is meant the sub-group of Group II which contains zinc, cadmium and mercury.) The ratios of the constituents of the catalyst mixture may be varied within fairly wide limits without seriously affecting the activity of the catalyst. The metals to be used in the metal uranyl carbonate may be derived from an element or elements occurring in Groups I, II and IV of Mendelejeifs periodic table. The elements which we have successfully used for this purpose include: calcium, strontium, barium, magnesium, zinc, silver, and lead.

In addition to the silver compound, metal uranyl compound, and compound of the first long period of the periodic table .(which 1ncludes the fourth and fifth periods) such as copper, nickel, iron or cobalt, we have found it advisable to have present another compound such as hydroxide of an element or elements occurring in Groups 11b to IV inclusive of the periodic table. Compounds of this type which we have successfully used are: beryllium. aluminium, thorium, and Z1!- conium hydroxides. These metal hydroxides appear to aid chiefly in hardening the catalysts, altho there is some indication that they also serve to some extent as promoters. Even without this effect, however, a catalyst containing a metal hydroxide of the-character specified lasts much longer than one not containing such a material.

A method of preparing our catalyst may be illustrated by the following example. It is distinctl understood, however, that we do not con no ourselves to this exact method nor to the amounts of materials mentioned. One-fifth am mol of uranyl nitrate, UO (NO 6H O; two-fifths gram mol of barium nitrate, Ba (NOQ two-fifths grammo] of silver nitrate, AgNO two-fifths gram mol of copper nitrate, Cu(NO and onefifth gram mol of aluminium nitrate, Al(NO .9H O are dissolved in four liters of distilled water. To this solution is next added a solution of 175 grams of potassium carbonate, K CO in two liters of water. The resulting precipitate is then washed by decantation with distilled water until free from nitrate ions. The precipitate is filtered, pressed dry, and then slowly dried at C. for 48 hours. The dried cake thus formed is broken up to 8-14 mesh and used for the catalytic conversion of alcohols to esters.

Instead of eli'ecting the precipitation as described above to give the carbonate form, the corresponding hydrate or phosphate, etc. compounds may be likewise obtained.

if found more convenient, for any reason, our improved catalysts may beprepared by thoroughly mixing in the form of a paste, or otherwise, the requisite amounts of the finely divided materials entering into their composition. For example, precipitated barium uranyl carbonate and aluminium hydroxide may be thoroughly mixed with silver carbonate and copper carbonate and the procedure outlined above, then followed. Satisfactory results may also be obtained by substituting the required amount of colloidal silver or colloidal metal of the first long peri- 0d of the periodic table for the salts of these two metals. After thorough mixing, the preparation of the catalyst mixture may then be completed as herein before described.

A number of method may be employed for preparing and sending the alcohol or alcohols over the catalyst. One method of accomplishing this is to force the said alcohol or alcohols over the catalyst by means of carbon dioxide or other inert gas under pressure. The liquid alcohol is in this process vaporized directly in the catalyst chamber. A second method of carrying out the process which we have found to be satisfactory is to bubble carbon dioxide gas thru the alcohol or alcohols which it is desired to convert, and pass the vapor thus obtained over the catayst.

In order to effect the conversion of alco- Qhols to esters by our new method, the alcohol or alcohols, alone or mixed with carbon diox- 1de or other inert gas or gases, is passed over catalysts repared as described, at tempera- .tures pre erably from 250 to 400 C., using a pressure of preferably from about 1 to about 200 atmospheres. Vhile it is possible to use temperatures outside of the range specified, we have found, that, as a rule, tem-' peraturcs below 250 C. give low conversions and temperatures above 400 C. give too many side reactions. We may, however, use temperatures as low as 200 C. and as high as 450 C.

The table given below shows data on the -conversion of n-butyl alcohol to butyl butyesters of the latter type rate under different conditions and with different catalyst combinations. In each case,

'20 c. c. of catalyst having the initial comwhich the operation is carried out. At the temperatures employed, the silver compound and the metal compounds of the first long period oi the periodic table used are largely reduced to their corresponding metallic forms.

Table II Temp., C.

essfie ae t;

Run

assesses assesses assesses Wehave found that it is possible to omit from our catalyst combinations either the silver compound or the compound of the metal appearing in the first long period of the periodic table and still obtain conversion of the alcohol or alcohols to the corresponding ester; in case, however, one of these constituents is omitted, much lower conversions,

and nerally, more unsatisfzactory results, are 0 tained. @mission of the silver compound, as a rule, gives poorer conversions than when the metal compound of the first long period of the periodic table is omitted instead of the silver compound For example, a catalyst composed initially of barium uranyl carbonate and nickel carbon ate, gives lower conversions than one comosed initiall a similar manner but containing initlall in addition to barium uranyl carbonate, oth silver carbonate and nickel carbonate, glves much higher yields and generally more satisfactory results than either of the former two combinations.

In the examples described above, we have only shown specific data relating to the production of butyl butyrate from butyla1- cohol. It is distinctl understood, however, that our process app ies also to the production of other similar esters such as ethyl acetate, propyl propionate, ethyl butyrate,

eth 1 r0 ionate pro yl butyrate, etc.;

y p p 7 being obtained when a mixture of alcohols is passed over our new catalyst.

Itis understood also that in preparing our catalyst combinations, we may include, if

of barium uranyl carbonate and silver car nate. A catalyst prepared in desired, more than one of each of the different classes of materials. I

Now having described our invention, what we claim as new and novel is:

1. The process of preparing esters from primary alcohols which comprises passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres, and temperatures from 200 C. to 450? 0., over compositions comprising initially barium uranyl carbonate, silver carbonate, copper carbonate,

and aluminium hydroxide.

2. The process of preparing esters from primary alcohols WhlCh comprises passing the catalyst compositions comprising initially metal uranyl compounds, a silver compound, and' a compound of a metal selected from the group consisting of copper, nickel, iron and cobalt.

bon atom, the step which comprises using as 4. In the process of preparing esters from primary alcohols having more {than one car bon atom, the step which comprises using as the catalyst compositions comprising metal uranyl compounds, metallic silver and a metal selected from the group'consisting of copper, nickel, iron, and cobalt.

5. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst compositions comprising metal uranyl carbonates, metallic silver and a metal selected from the group consisting of copper, nickel, iron and cobalt.

6. In the process of preparing esters from primary alcohols having more than one caron atom, the step which comprises using as the catalyst compositions comprising initially metal uranyl carbonates, a silver compound, and' a compound of a metal selected from the group consisting of copper, nickel, iron and cobalt.

'Z. In the process of preparing esters from pgimary alcohols having more than one carn atom, the step which comprises using as the catalyst compositions comprising initially uranyl compounds of metals selected from the group consisting of calcium, stron- 'tium, barium,.magnesium, zinc, silver and lead; a silver compound, and a compound nickel, iron and cobalt.

selected from the group consisting of copper,

as the catalyst compositions comprising initially uranyl compounds of metals selected from the group consistingof calcium, strontium, barium, magnesium, zinc, silver and lead; silver carbonate, and a metal selected from the group consisting of copper, nickel, iron and cobalt.

9. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst compositions comprising initially metal uranyl compounds, a silver compound, compounds selected from the group consisting of copper, nickel, iron and cobalt; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryllium.

10. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst compositions comprising metal uranyl compounds, metallic silver, metals selected from the group consisting of copper,

nickel, iron and cobalt; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryl lium. 11. In the process of preparing esters from primary alcohols having more than one carbon atom, the step which comprises using as the catalyst compositions comprising initially uranyl carbonates of metals selected from the group consisting of calcium, strontium, barium, magnesium, zinc, silver and lead; a silver compound, compounds selected from the group consisting of copper, nickel, iron and cobalt; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryllium.

12. In the process of preparing esters from rimary alcohols having more than one caron atom, the step which comprises using as the catalyst compositions comprising uranyl carbonates of metals selected from the group consisting of calcium, strontium, barium, magnesium, zinc, silver and lead; metallic silver, metals selected from the group consisting of copper, nickel, iron and cobalt; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryllium.

13. In the process of preparing esters from rimary alcohols having more than one caroon atom, the steps which comprise passing; said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 C., over compositions comprising initially metal uranyl compounds, a silver compound, and a compound of a metal selected from the group consisting of copper, nickel, iron and cobalt.

14-. In the process of preparing esters from rimary alcohols having more than one carbon atom, the steps which comprise passing 7 said alcohols in the vapor form, at pressures from 1 to 200 atmospheres, and temperatures from 200 C. to 450 C. over compositions comprising metal uranyl compounds, metallic silver and a metal selected from the group consisting of copper, nickel, iron and cobalt.

15. In the process of preparing esters from primary alcohols having more than one carbon atom, the steps which comprise passing said alcohols in the vapor form, at -pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 C. over compositions comprising metal uranyl carbo-- nates, metallic silver and a metal selected from the group consisting of copper, nickel, iron, and cobalt.

16. In the process of preparing esters from primary alcohols having more than one carbon, a om, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 C. over compositions comprising initiallymetal uranyl carbonates, a silver compound, and a compound of a metal selected from the group consisting of copper, nickel, iron and cobalt.

17. 'In the process of preparing esters from primary alcohols having more than one carbon atom, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 C. over compositions 'comprising initially uranyl compounds of metals selected from the group consisting of calcium, strontium, barium, magnesium, zinc, silver and lead; a silver compound, and a compound selected from the group consisting of copper, nickel, iron and cobalt.

18. In the process of preparing esters from primary alcohols having more than one carbon atom, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 (1, over compositions comprising initially uranyl compounds of metals selected from the group consisting of calcium, strontium, barium, magnesium, zinc, silver, and lead; silver carbonate and a metal selected from the group consisting of copper, nickel, iron and cobalt.

19. In the process of preparing esters from primary alcohols having more than one carbon atom, the steps which comprise passing said alcohol in the vapor form at ressures from 1 to 200 atmospheres and temgeratures strontium, barium, magnesium, zinc,'silver and lead; a sllver compound, compounds se lected from the group consisting of copper, nickel, iron and cobalt; and hydroxides of metals selected from the group consisting of aluminium, thorium, zirconium and beryllium. p

22. In the process of preparing esters from primary alcohols havingvmore than one carbon atom, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C..to 450 C. over compositions 1 comprising uranyl carbonates of metals selected from the group consisting of calcium,

strontium, barium, magnesium, zinc, silver and lead; copper carbonate and aluminium hydroxide.

23. In the process of preparing esters from primary alcohols having more than one carbon atom, the steps which comprise passing said alcohols in the vapor form, at pressures from 1 to 200 atmospheres and temperatures from 200 C. to 450 C. over compositions comprising 'uranyl carbonatesof metals selected from the group consisting of calcium, strontium, barium, magnesium, zinc, silver and lead; metallic copper, metallic silver, and

tures'.

aluminium hydroxide.

In testimony whereof We afix our signa- JEROME MARTIN. IGNACE J. CH, 

